Administration of the synthetic, crystalline cannabinoid, nabilone, and the potent dimethylheptyl derivative of (-)-delta-8-tetrahydrocannabinol reduces the turnover rate of acetylcholine in the hippocampus and reduces the turnover rate of GABA in the septum. As a working hypothesis we suggest that a group of inhibitory GABA-containing interneurons impinges on a second smaller group of inhibitory GABA containing interneurons which modulates the activity of cholinergic cell bodies located in the medial septum whose long axons project to hippocampus.